The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Two clocks are syntonized if the duration of one second (i.e., one unit of time) is the same for both clocks. When two clocks are syntonized, the time measured by each clock advances at the same rate. The two clocks may or may not share the same epoch (i.e., origin of a timescale). Two clocks are synchronized to a specified uncertainty if (1) the two clocks have the same epoch, and (2) measurements of time of a single event at an arbitrary time made using the two clocks differ by no more than the specified uncertainty.
Network devices use clock signals generated by local oscillators to calculate time of day and to timestamp packets with the time of day. The timing of the clock signals can differ from one network device to another due to variations in the local oscillators. For each network device to have the same time of day, the clock signals of the network devices need to be synchronized.
Various techniques are used to synchronize the clock signals of network devices. Within a domain, the clock signals ultimately derive respective timing from a grandmaster clock, which is the ultimate source of time for clock synchronization. The clock signals typically derive the timing from the grandmaster clock using a precision time protocol (PTP). The PTP is defined in IEEE Std 1588™-2008 standard, which is incorporated herein by reference in its entirety.